The present invention relates to seed planters for dispensing individual seeds at a controlled rate into a seed furrow, and specifically to seed planters that employ vacuum systems for metering the seeds.
Seed planters dispense seeds at a controlled rate into a seed furrow as a planter is advanced along the ground. In a typical arrangement, a tractor is coupled to tow a tool bar to which is attached, in a parallel spaced part relationship, a plurality of planting units.
Each planting unit typically includes a seed hopper holding seeds and communicating with a seed meter for dispensing seeds at a controlled rate as the planting unit moves over the ground. The planting unit may include on its lower surface a furrow opening disk for opening a furrow for the seeds, a furrow closing disk for closing the furrow about the seeds, and a trailing wheel that tamps down the earth about the furrow.
The seed metering unit must pick individual seeds from the hopper and deliver them between the furrow opening disk and the furrow closing disk at a controlled rate. One method of accomplishing this task with seeds of different sizes and shapes uses a disk with a plurality of openings that rotates past a seed chamber. A vacuum draws air through the openings in the disk to trap individual seeds within each opening for delivery into a second location for release.
The vacuum for the seed metering device may be provided, for example, by a blower driven by an hydraulic motor attached to the hydraulic system of the tractor. The motor is sized to provide a sufficient vacuum pressure at an air flow rate that might be anticipated when each disk for each planting unit is empty of seeds, and therefore under a condition of minimum back resistance to the blower. After seeds begin to fill the holes, a lower flow rate is required.